1. Field of the Invention
This invention relates to a process for making a copolymer of maleic anhydride and an alkyl vinyl ether, and, more particularly, to a process for making such copolymers of advantageously high specific viscosity.
2. Description of the Prior Art
British Patent 906,230 described the preparation of copolymers of maleic anhydride and methyl vinyl ether in benzene as solvent. Example 1 also disclosed a copolymerization process in absence of solvent in which powdered maleic anhydride, methyl vinyl ether and initiator were precharged into an autoclave and reacted at 55° C. The specific viscosity (SV) of the product, however, was only 3.45 (1% in methyl ethyl ketone, MEK).
Other processes and copolymer products described previously included U.S. Pat. Nos. 4,952,558; 5,034,488; 5,047,490; 5,874,510; 6,624,271; 6,184,325; and Re 36,657.
However, none of these processes are suitable for making such copolymers of advantageously high specific viscosity (and, correspondingly, high molecular weights).
Accordingly, it is an object of this invention to provide a process for making copolymers of maleic anhydride and an alkyl vinyl ether having high specific viscosities.
A feature of this invention is a process for making such copolymers in which the copolymerization is carried out in the presence of added acetylene.
Another feature of the invention is the provision of copolymers of maleic anhydride and methyl vinyl ether having a specific viscosity of at least 7, preferably at least 10 (1% in MEK, 25° C.), uncrosslinked or crosslinked.
These and other objects and features of the invention will be made apparent from the following description.